D ÁN TH Y I N TRUNG S N TRUNG SON HYDROPOWER PROJECT THI T K K THU T TECHNICAL DESIGN MÔ HÌNH V N HÀNH H CH A OPERATION MODEL OF RESERVOIR

Public Disclosure Authorized Public Disclosure Authorized Public Disclosure Authorized Public Disclosure Authorized ISO 9001:0 VIETNAM ELECTRICITY POWER ENGINEERING CONSULTING JOINT STOCK COMPANY 4 Project: T.02.04 D ÁN TH Y I N TRUNG S N TRUNG SON HYDROPOWER PROJECT THI T K K THU T TECHNICAL DESIGN MÔ HÌNH V N HÀNH H CH A OPERATION MODEL OF RESERVOIR Nha Trang City, July 2010

CONTRUTORS No. Full name Task Signature 1 Vuong Anh Dung Preparing chapter 3 2 Nguyen Van De Preparing chapter 1 3 Nguyen Tien Phong Preparing chapter 2 4 Truong Hoai The Tuyen Preparing chapter 4 5 Phung Ngoc Tam Preparing chapter 4 6 Tran Minh Kha Checking Contributor i

CONTENTS The document is established in below volume Operation model of reservoir Contents ii

TABLE OF CONTENTS CHAPTER 1: ANNUAL FLOW SPECIFIC CALCULATION 1 1.1 FLOW CONDITION CALCULATION ON BASIN 1 1.2 CALCULATION OF ANNUAL AVERAGE FLOW IN LONG-TERM PERIOD AT TRUNG SON HYDROLOGICAL 5 1.3 DESIGN ANNUAL FLOW DISTRUTION AND ANNUAL FREQUENCY 10 1.4 DAILY FLOW RANGE TO TRUNG SON HYDROPOWER DAMSITE 11 CHAPTER 2: RESERVOIR ANALYSIS AND SIMULATION 12 2.1 PLANNING HYDROPOWER PROJECTS CASCADES ON MA RIVER 12 2.2 ADDITIONAL PLANNING HYDROPOWER PROJECTS CASCADES ON MA RIVER 13 2.3 MAIN PARAMETERS OF TRUNG SON HYDROPOWER PROJECT TECHNICAL DESIGN STAGE 14 2.4 DATA FOR CALCULATION 16 2.5 CALCULATION, SIMULATION OF RESERVOIR 18 2.6 WITHOUT THANH SON RESERVOIR IN DOWNSTREAM OF TRUNG SON HYDROPOWER PLANT (CASE 1) 18 2.7 DOWNSTREAM WITH THANH SON RESERVOIR (CASE 2) 37 CHAPTER 3: WATER SUPPLY DEMAND FOR DOWNSTREAM 40 3.1 WATER DEMAND AT DOWNSTREAM 40 3.2 ENVIRONMENT FLOW RELEASE MEASURES 42 3.3 DISCHARGE OF WATER DURING OPERATION PROCESS 42 3.4 DISCHARGE OF MUD AND SAND 43 3.5 RESERVOIR DEWATERING 43 3.6 CONCLUSION 43 CHAPTER 4: RESERVOIR AND DOWNSTREAM LANDSLIDE POSSILITY FORECAST 44 4.1 RESERVOIR BANK LANDSIDE POSSILITY 44 4.2 EROSION RIVER BED OF RESERVOIR DOWNSTREAM 47 4.3 SLIDING AT BANKS OF DOWNSTREAM 48 APPENDIX... 48 - Appendix calculation of hydrographical - Location chart of section calculation stability - Appendix calculation of reservoir bank stability - Appendix calculation reservoir downstream stability Table of contents iii

Chapter 1: ANNUAL FLOW SPECIFIC CALCULATION 1.1 FLOW CONDITION CALCULATION ON BASIN Trung Son Hydrological station has been built and put into operation since Oct 4, it is located about 400m downstream of Trung Son dam site. It measures all the factors: precipitation, water level, discharge, flood.. The difference between the basin areas of the damsites and Trung Son station is not remarkable, we can consider the flow to Trung Son hydrological station is equal to the flow to the damsite. Thus, the calculation result at the Trung Son hydrological station is equal to the calculation result at the damsites. There are hydrological stations at the upstream of Ma river: Muong Lat (water level, precipitation), Xa La (precipitation, water level, temperature, discharge..); at the downstream of the river, there are hydrological stations such as:hoi Xuan (discharge, 1965 1970, water level, 1962 8), Cam Thuy (water level, 1957 8; discharge 1957 1976, 1995 8) besides, there are other hydrological stations at the tributaries such as Nam Ty, Nam Cong, Cua Dat, Lang Chanh... Due to the non-sychronous data and lack of data continuity observed at those stations, the flow calculation of Trung Son hydrological station mainly depends on the analysis method of flow correlation, co-ordinating with precipitation distribution and flow module analysis. The method is carried out between Trung Son hydrological station and 3 other hydrological stations that measure the discharge namely Cam Thuy, Hoi Xuan, Xa La. 1.1.1. Recovering the flow data at Cam Thuy Hydrological Station Cam Thuy hydrological station measured the water level and discharge from 1957 to 1976 with the standard of Level 1 hydrological station. From 1977 to 1994, it moved some kilometers downstream and downgraded, only measured water level. From 1995 up until now (8), it moved to the old location and continued observing according to the station of level 1 station. Now, the water level data at Cam Thuy from 1977 to 1994 has been correlatively calculated by Hydro-meteorological General Bureau and brought back to water elevation of the old Cam Thuy hydrological station (it is also the location now) to unify the elevation. The relationship curve Q=F(H) is synthetized at Cam Thuy hydrological station in 1973, 1975, 1995. Then the discharge is interpolated from the relation Q=F(H) and daily water level data in 1977 1994 Flow data chaining advent barrage calculation 1

After the calculation, we have the daily flow at Cam Thuy hydrological station from 1957 to 8, average long-term flow is Q tb =346 m 3 /s. Summarization of monthly observed flow and calculated flow from 1957 to 8 at Cam Thuy hydrological station are shown in Table 1 of the Appendices. 1.1.2. Recovering data at Hoi Xuan hydrological Station Hoi Xuan hydrological station has been measuring the water level from 1962 up until now (8), it measured the discharge from 1965 to 1970. The recovering and addition to this flow data at Hoi Xuan hydrological station is carried out through 3 methods: 1) Calculation according to monthly average discharge in correlation with Cam Thuy hydrological station: The monthly average discharge correlation between Cam Thuy and Hoi Xuan hydrological stations from 1965 to 1970 Flood season: Correlation coefficient =0.989; Correlation equation: Q Hoi Xuan = 0.861*Q Cam Thuy 5.14 (m 3 /s) Dry season: Correlation coefficient =0.984; Correlation equation: Q Hoi Xuan = 0.823*Q Cam Thuy + 4.864 (m 3 /s) From this equation and the monthly average discharge at Cam Thuy hydrological station, we can calculate the data chain at Hoi Xuan hydrological station from 1957 1964, 1971 8. According to that, the average annual discharge in long-term period at Hoi Xuan is 295 m 3 /s. 2) Calculation according to daily average discharge in correlation with Cam Thuy hydrological station: The daily average discharge correlation between Cam Thuy and Hoi Xuan hydrological stations from 1965 to 1970 January: the coefficient of =0.890. Correlation equation: Q Hoi Xuan = 0.694*Q Cam Thuy + 18.79 (m 3 /s) February: the coefficient of =0.900. Correlation equation: Q Hoi Xuan = 0.625*Q Cam Thuy + 25.09 (m 3 /s) March: the coefficient of =0.933. Correlation equation: Q Hoi Xuan = 0.770*Q Cam Thuy + 9.632 (m 3 /s) April: the coefficient of =0.927. Correlation equation: Flow data chaining advent barrage calculation 2

Q Hoi Xuan = 0.825*Q Cam Thuy + 7.81 May: the coefficient of =0,895. Correlation equation: Q Hoi Xuan = 0.704*Q Cam Thuy + 19.31 June: the coefficient of =0.942. Correlation equation: Q Hoi Xuan = 0.819*Q Cam Thuy + 9.512 July: the coefficient of =0.890. Correlation equation: Q Hoi Xuan = 0.765*Q Cam Thuy + 54.43 August: the coefficient of =0,965. Correlation equation: Q Hoi Xuan = 0.755*Q Cam Thuy + 84.42 (m 3 /s) (m 3 /s) (m 3 /s) (m 3 /s) (m 3 /s) September: the coefficient of =0.952. Correlation equation: Q Hoi Xuan = 0.740*Q Cam Thuy + 55.17 (m 3 /s) October: the coefficient of =0.956. Correlation equation: Q Hoi Xuan = 0.646*Q Cam Thuy + 61.63 (m 3 /s) November: the coefficient of =0.936. Correlation equation: Q Hoi Xuan = 0.590*Q Cam Thuy + 59.62 (m 3 /s) December: the coefficient of =0.902. Correlation equation: Q Hoi Xuan = 0.936*Q Cam Thuy 8.29 (m 3 /s) Based on these equations and the daily average discharge at Cam Thuy hydrological station can calculate data chain at Hoi Xuan hydrological station from 1957 1964, 1971 8. Thence, the long-term average discharge at Hoi Xuan is 289 m 3 /s. 3) Calculation according to water level data and the relation Q=F(H) Water level data at Hoi Xuan hydrological station from 1957-1961 was recovered from water level data at Cam Thuy hydrological station by correlation method. Cam Thuy hydrological station measured discharge and level water from 1957-1976. After, it s displaced to downstream and measured level water only. In 1995, it s displaced again to return the initial location, and upgraded to measure both discharge and level water. The level water data at Cam Thuy hydrological station from 1977-1994 is calculated and converted. Hence, daily average level water in every month in correlation between Cam Thuy hydrological station and Hoi Xuan hydrological station is carried out from 1962-1976. Flow data chaining advent barrage calculation 3

January: the coefficient of =0.868. Correlation equation: H Hoi Xuan = 1.56*H Cam Thuy + 3,386 (cm) February: the coefficient of =0.831. Correlation equation: H Hoi Xuan = 1.15*H Cam Thuy + 3863 (cm) March: the coefficient of =0.889. Correlation equation: H Hoi Xuan = 1.55*H Cam Thuy + 3407 (cm) April: the coefficient of =0.927. Correlation equation: H Hoi Xuan = 1.44*H Cam Thuy + 3526 (cm) May: the coefficient of =0.840. Correlation equation: H Hoi Xuan = 1.06*H Cam Thuy + 3972 (cm) June: the coefficient of =0.957. Correlation equation: H Hoi Xuan = 1.08*H Cam Thuy + 3960 (cm) July: the coefficient of =0.962. Correlation equation: H Hoi Xuan = 0.922*H Cam Thuy +4167 (cm) August: the coefficient of =0.936. Correlation equation: H Hoi Xuan = 0.912*H Cam Thuy + 4188 (cm) September: the coefficient of =0.965. Correlation equation: H Hoi Xuan = 0.936*H Cam Thuy + 4139 (cm) October: the coefficient of =0.954. Correlation equation: H Hoi Xuan = 0.887*H Cam Thuy + 4202 (cm) November: the coefficient of =0.900. Correlation equation: H Hoi Xuan = 1.02*H Cam Thuy + 4031 (cm) December: the coefficient of =0.8. Correlation equation: H Hoi Xuan = 1.61*H Cam Thuy + 3332 (cm) Based on these equations and daily average level water at Cam Thuy hydrological station can calculate data chain at Hoi Xuan hydrological station from 1957-1961 The relation curve Q=F(H) is synthesized from Hoi Xuan s observed data in 1965-1970. Then, the daily flow data chain at Hoi Xuan hydrological station from 1957 1964 and 1971-8 is calculated based on the over relation curve Q=F(H) and water level data. Hence, the long-term average discharge at Hoi Xuan is 290 m 3 /s Flow data chaining advent barrage calculation 4

Over results (calculated by three methods) are not different much. The daily average discharge correlation method with Cam Thuy hydrological station (Method 2) reflects the reality of the river flow, having high coefficient, giving values close to values calculated by water level and the relation curve Q=F(H) method, and reducing the errors due to the changes of river bed through many years. Thus, it is chosen. Hence, the long-term average flow at Hoi Xuan hydrological station is 289 m 3 /s. The synthesized results of monthly flow data chain at Hoi Xuan hydrological station is in Table 2 in the appendices. 1.2 CALCULATION OF ANNUAL AVERAGE FLOW IN LONG-TERM PERIOD AT TRUNG SON HYDROLOGICAL 1.2.1. Daily average water level data recovery method Create the correlation relationship of daily average water level between Trung Son and Hoi Xuan hydrological stations from 01 January 5 to 31 December 8, the achieved correlation coefficient is =0,949 and correlation equation is as follows: H Trung Son = 0.707*H Hoi Xuan + 5131 (cm) February: the coefficient of =0.914. Correlation equation: H Trung Son = 0.328*H Hoi Xuan + 7105 (cm) June: the coefficient of =0.914. Correlation equation: H Trung Son = 0.637*H Hoi Xuan + 5493 (cm) July: the coefficient of =0.958. Correlation equation: H Trung Son = 0.820*H Hoi Xuan + 4525 (cm) August: the coefficient of =0.947. Correlation equation: H Trung Son = 0.934*H Hoi Xuan + 3919 (cm) September: the coefficient of =0.899. Correlation equation: H Trung Son = 0.883*H Hoi Xuan + 4194 (cm) October: the coefficient of =0.935. Correlation equation: H Trung Son = 0.634*H Hoi Xuan + 5520 (cm) November: the coefficient of =0.918. Correlation equation: H Trung Son = 0.565*H Hoi Xuan + 5879 (cm) December: the coefficient of =0.928. Correlation equation: H Trung Son = 0.534*H Hoi Xuan + 6038 (cm) Flow data chaining advent barrage calculation 5

The coefficient of Jan, Mar, Apr, May months is smaller than 0.8. Thus, correlation equation of this are taken general correlation equation: H Trung Son = 0.707*H Hoi Xuan + 5131 (cm) With these equations and the water level data at Hoi Xuan can recover the water level data at Trung Son in the period of 1957-4. The correlation curve Q=F(H) at Trung Son station is synthetized from observed data in the period 5 8. Then, calculating the daily flow data chain at Trung Son station in the period of 1957 4 from the water level data and the synthetized relationship Q=F(H). Hence, the long-term average discharge is 216 m 3 /s. 1.2.2. Flow correlation method with Cam Thuy hydrological station - Creating the monthly average discharge correlation between Cam Thuy and Trung Son stations from January 5 to December 8 Flood season: Correlation coefficient is =0.954. Correlation equation: Q Trung Son = 0.636*Q Cam Thuy - 3,27 (m 3 /s) Dry season: Correlation coefficient is =0.941. Correlation equation: Q Trung Son = 0.506*Q Cam Thuy + 20,45 (m 3 /s) With these equations and discharge at Cam Thuy hydrological station can calculate the flow data chain at Trung Son station from 1957-4. Hence, the average discharge in long-term period (1957-8) is 218 m 3 /s. - Creating the daily average discharge correlation between Cam Thuy and Trung Son stations from January 5 to December 8 Average calculation result from 01 January 5 to 31 December 8, correlation coefficient is =0,922. Correlation equation is as below: Q Trung Son = 0.545*Q Cam Thuy + 30.6 (m 3 /s) January: the coefficient of =0.947. Correlation equation: Q Trung Son = 0.654*Q Cam Thuy 1.04 (m 3 /s) February: the coefficient of =0.876. Correlation equation: Q Trung Son = 0.745*Q Cam Thuy 11.69 (m 3 /s) March: the coefficient of =0.852. Correlation equation: Q Trung Son = 0.651*Q Cam Thuy 2.43 (m 3 /s) Flow data chaining advent barrage calculation 6

April: The coefficient of April is smaller than 0.8. Thus, the correlation equation of this is taken genera correlation equation: Q Trung Son = 0.545*Q Cam Thuy + 30.6 (m 3 /s) May: The coefficient of May is smaller than 0.8. Thus, the correlation equation of this is taken genera correlation equation: Q Trung Son = 0.545*Q Cam Thuy + 30.6 (m 3 /s) June: the coefficient of =0.901. Correlation equation: Q Trung Son = 0.674*Q Cam Thuy 23.08 (m 3 /s) July: the coefficient of =0.871. Correlation equation: Q Trung Son = 0.661*Q Cam Thuy 7.65 (m 3 /s) August: the coefficient of =0.899. Correlation equation: Q Trung Son = 0.622*Q Cam Thuy + 44.74 (m 3 /s) September: the coefficient of =0.876. Correlation equation: Q Trung Son = 0.512*Q Cam Thuy + 103.23 (m 3 /s) October: the coefficient of =0.936. Correlation equation: Q Trung Son = 0.387*Q Cam Thuy + 112.22 (m 3 /s) November: the coefficient of =0.882. Correlation equation: Q Trung Son = 0.341*Q Cam Thuy + 95.14 (m 3 /s) December: the coefficient of =0.971. Correlation equation: Q Trung Son = 0.756*Q Cam Thuy 11.47 (m 3 /s) Calculate the daily discharge data chain at Trung Son station in the period of 1957 4 based on these correlation equations and daily average discharge at Cam Thuy hydrological station. Hence, average annual discharge in long-term period is 229 m 3 /s. 1.2.3. Flow correlation method with Xa La station Creating the monthly average discharge correlation between Xa La and Trung Son station from January 5 to December 8 In flood season, the coefficient is =0.758. It is too small to calculate and recover flow data at Trung Son station. So, data in flood months is recovered and calculated by correlation relation among months in the whole year. The synthesized coefficient of Flow data chaining advent barrage calculation 7

months from 5 to 8 between Xa La and Trung Son stations is =0.875. The correlation equation is as below: Q Trung Son = 1.638*Q Xa La + 45.61 (m 3 /s) In dry season, the coefficient =0.893. The correlation equation: Q Trung Son = 1.75*Q Xa La + 26.17 (m 3 /s) Based on these equations and discharge at Xa La station can calculate flow data chain at Trung Son station from 1961-4. Hence, average annual discharge in longterm period at Trung Son is 235 m 3 /s. 1.2.4. Flow correlation method with Hoi Xuan hydrological station Creating the monthly average discharge in correlation between Hoi Xuan and Trung Son station from I/5 to XII/8. In flood season, the coefficient =0.968. The correlation equation: Q Trung Son = 0.836*Q Hoi Xuan 34.78 (m 3 /s) In dry season, the coefficient ( =0.692) is too small to correspond with calculating and recovering flow data at Trung Son station. So, data in dry months is recovered by correlative relation among months in the whole year. The synthesized coefficient of months from 5 to 8 between Hoi Xuan and Trung Son is =0.964. The correlation equation: Q Trung Son = 0.1*Q Hoi Xuan 20.01 (m 3 /s) From these equations and discharge at Hoi Xuan hydrological station, we can flow data chain at Trung Son station from 1957 to 4. According to that, average annual discharge in long-term period at Trung Son is 213 m 3 /s. 1.2.5. Flow module analysis method The flow module distribution on Ma river is as follows: Table 1.1: The flow module at some stations in Ma river basin Station Area (km 2 ) Period Q aver (m 3 /s) M (l/s/km 2 ) Cam Thuy 18,879 1957 8 346 18.3 Hoi Xuan 16,850 1957 8 289 17.2 Xa La 6,430 1961 8 18.7 Flow data chaining advent barrage calculation 8

Trung Son station is located between Hoi Xuan and Xa La stations, the flow module of Trung Son station is M= 17.5 l/s/km 2, calculated by interpolation method. Thus, can calculate the annual average discharge at Trung Son station Q= 257 m 3 /s. The flow data at Hoi Xuan hydrological station is recovered mainly; data at Cam Thuy and Xa La stations is more adequate. Use interpolation method to calculate flow module to Trung Son station from relation between area and flow module of Cam Thuy and Xa La stations. According to this method, the flow module to Trung Son station will be M= 18.4 l/s/km 2. Thus, the long-term average discharge at Trung Son station can calculated Q= 270 m 3 /s. The analysis of precipitation changes in the mid-areas from Cam Thuy to Hoi Xuan and from Hoi Xuan to Trung Son shows that the average annual rainfall in longterm period from Cam Thuy to Hoi Xuan is about 1850 mm; from Hoi Xuan to Trung Son is about 0 mm. The application of area rate method plus basin average rainfall rate method due to mid-basin from Cam Thuy to Hoi Xuan. The average annual discharge at Trung Son will be equal to the average annual discharge in long-term period at Hoi Xuan minus the mid-area. Q Trung Son = 236 m 3 /s. 1.2.6. Analyse, choose the results of flow calculation to Trung Son dam site Table 1.2: Synthesized results of annual average flow in long-term period at Trung Son station according to different methods Method Q 0 M 0 1. Interpolating Water data and the relationship Q=F(H) 216 14.7 2. Monthly average discharge correlation with Cam Thuy hydrological station 218 14.9 2. Daily average discharge correlation with Cam Thuy hydrological station 229 15.6 3. Discharge correlation with Xa La station 235 16.0 4. Discharge correlation with Hoi Xuan hydrological station 213 14.5 5. Interpolating flow module Hoi Xuan Xa La 257 17.5 6. Interpolating flow module Cam Thuy Xa La 270 18.4 7. Mid-area discharge deduction from Hoi Xuan to Trung 236 16.1 Average 234 16.0 Due to the complexity of the precipitation and flow distribution on Ma river the part on Laos territory has less rainfall than on Vietnam, so the calculation results by the different methods will be different as well. Each method has its own advantages and disadvantages. The water level data retrieval method at Trung Son station from Flow data chaining advent barrage calculation 9

Hoi Xuan hydrological station is easy to cause errors because the parallel measured water level data chain is short, the water level in serious flood years isn t measured sufficiently and the cross sections are changed after years. The data chain from 1977 1994 at Cam Thuy hydrological station is achieved through calculation and recovery from the water level and relationship Q=F(H), the parallel measured data chain between Cam Thuy and Trung Son is still short, thus the monthly average flow correlation method between Trung Son and Cam Thuy is not fully trusted. It is similar to above mention, the correlation method between Trung Son and Xa La also have a short parallel observed data chain; their correlation coefficient is not much great; Ma river, after flowing cross Laos territory where rainfall is small, flow amplitude changes a little bit, thus results achieved by this method isn t completely trusted. The method considering flow module progress based on the measured data at the hydrological stations on Ma river basin, considering the effect of rainfall distribution on the basin, can determine quite exactly the long-term average flow but determining exactly the average annual precipitation in the basin is difficult, so it is difficult to determine exactly the annual flow. The average flow value achieved from these above methods are Q Trung Son = 234 m 3 /s, M Trung Son = 16,0 l/s/km 2, these values are equal to the discharge depreation method at mid-area with the mean rain fall (Q Trung S n = 236 m 3 /s), nearly the same with the result of discharge correlation with Xa La station method (Q Trung S n = 235 m 3 /s). As change a number of calculating years, the average annual runoff value at Trung Son station fluctuates around at 235 m 3 /s, recommend to choose this result Q 0 Trung Son = 235 m 3 /s 1.3 DESIGN ANNUAL FLOW DISTRUTION AND ANNUAL FREQUENCY 1.3.1. Monthy average flow range To achieve a nearly correct flow distribution at Trung Son station, the flow distribution following the daily average flow correlation wih Cam Thuy hydrological station has been used, with the modification according to the chosen average flow in the long-term period. The results are as in table 3, Appendixes. 1.3.2. Seasonal flow rate Based on the observed and calculated flow data at Trung Son station (1957 7) carry out the seasonal flow classification according to the over-average standard, the results achieved are: flood season starts from June, ends in October; dry Flow data chaining advent barrage calculation 10

season starts from November, ends in next May. The results are in table 4 in the appendices. 1.4 DAILY FLOW RANGE TO TRUNG SON HYDROPOWER DAMSITE By correlation relation analysis, the flow correlation in Ma river at Trung Son with Hoi Xuan and Cam Thuy is better than with Xa La. This difference shows that the natural condition in Ma river is: heavy rain in the upstream, small rain in Laos territory and gradually heavier from Trung Son to Cam Thuy, the area difference between Trung Son and Hoi Xuan, Cam Thuy is smaller than between Trung Son and Xa La. Hoi Xuan hydrological station has an short observed daily discharge data chain (1965-1970), the data of the remaining years (1957 1964, 1971 8) are achieved by recovering calculation, the old relation Q=F(H) (synthetized from 1965-1970) is not measured to check the changes in the following years, thus it is easily to cause errors. Cam Thuy hydrological station has a longer observed data chain (1957 1976, 1995 8), the calculated recovering flow data chain (1977 1994) has a close base, the relation Q= F(H) is synthetized according to the years before 1977 and after 1994. Thus, flow distribution reflects the reality, can trust well, and choose to calculate flow distribution at Trung Son hydrological station. The daily discharge chain (1957-4) at Trung Son station is chosen according to daily average discharge correlation calculation results with Cam Thuy hydrological station, in which: using separate correlation equations for each month and calculating is in the adjustment to get average annual discharge at Trung Son, Q aver =235 m 3 /s. The synthetized results of daily average discharge at Trung Son station are summarized in the report of Reservoir operation process. Flow data chaining advent barrage calculation 11

Chapter 2: RESERVOIR ANALYSIS AND SIMULATION 2.1 PLANNING HYDROPOWER PROJECTS CASCADES ON MA RIVER On March 31, 5, Ministry of Industry (presently called as Ministry of Industry and Trade) issued decision No.1195/Q -NLDK, concerning approval on planning of hydropower cascades on Ma river, main contents as below: - Exploiting scheme of hydropower cascades projects and main task of hydropower projects on Ma river: + On Ma river tributary, there are 05 multi-purposes hydropower reservoirs projects Pa Ma hydropower project, with normal water level at 455m, installed capacity of MW; main tasks are water supply and flood control; combined with electric power generation. Huoi Tao hydropower project: normal water level at 3m, installed capacity of MW; main task are water supply and flood control; combined with electric power generation. Trung Son hydropower project: normal water level at m, installed capacity of 2MW; main task are electric power generation and flood control. Hoi Xuan hydropower project: normal water level at m, installed capacity of 92MW; main task are electric power generation and water supply. Cam Ngoc hydropower project: normal water level at 50m, installed capacity of 145MW; main tasks are water supply, combined with electric power generation. + In Chu River tributary, there are 02 hydropower projects Hua Na hydropower project, normal water level at 240m, installed capacity of MW; main tasks are electric power generation and flood control. Cua Dat hydropower project, normal water level at 119m, installed capacity of 97MW. This project is under operation. Main tasks are water supply and flood control, combined with electric power generation. - Flood control storage capacity at respective reservoirs + Total flood control storage capacity on Ma River is estimated approximately 700 million m 3 respectively at Pa Ma reservoir (about million m 3 ), Huoi Tao (about 300 million m 3 ), Trung Son reservoir (maximum million m 3 ). It is required to substantiate presisely in details the distribution flood control storage capacity between cascades in Ma River when establishing Feasibility Study, with consideration of all actual topographical, geological condition of the project as well as in the downstream area, proposed other Analysis and simulation of reservoir 12

reservoirs in Ma River construction time according to water resource development program, to ensure economical and technical requirements. + Total flood control storage capacity on Chu River is estimated approximately at 400 million m 3, respectively at Cua Dat hydropower reservoir at 300 million m 3 and Hua Na hydropower reservoir at million m 3 - Priority sequence construction of projects: + Hydropower projects to be constructed in the first stage: Cua Dat and Hua Na projects on Chu River, Trung Son project in Ma River + Hydropower projects to be studied as multipurpose: Hoi Xuan, Cam Ngoc, Pa Ma, Huoi Tao projects on Ma river (detail at appendix: attachment legal documents) 2.2 ADDITIONAL PLANNING HYDROPOWER PROJECTS CASCADES ON MA RIVER On April 18, 8, Ministry of Industry and Trade issued decision No.2383/Q -BCT converning approval on additional planning hydropower project cascades on Ma River, with main contents, as below: - Additional planning Thanh Son hydropower project on Ma river cascades was approved by Ministry of Industry (presently called as Ministry of Industry and Trade) at decision No. 1195/Q -NLDK dated on March 31, 5 with main contents, as below: + Construction site: On the main stream of Ma river at the Thanh Son and Trung Thanh communes, Quan Hoa district, Thanh Hoa Province, with coordinates (VN-0 system): X= 2 277 459.6 and Y= 490 006.9 + Task and exploiting scheme of project: Project has main task is power generation. The hyro energy exploiting scheme consisting of main dam and spillway with dam-toe hydropower plant type. + Main parameters of project: Catchment basin area calculated to damsite Flv = 13.275Km 2, annual average discharge Q 0 = 246 m 3 /s, normal water level = 89m, tailrace water level MNHL min = 78.5m, rated water head H tt = 8.8m and installed capacity N lm = 37MW - Investment of Thanh Son hydropower project must be complied with socioeconomic development plans, land and water resource use plans, electric power development plan in the Thanh Hoa province; synchronously with power load development situation as well as investment of electric power transmission network in region as planned by Vietnam Electricity. - In feasibility study stage of Thanh Son hydropower project, Thanh Hoa Provincial People s Committee shall be responsible to give directives, inspection and consideration of below issues: + Additional investigation, survey on natural conditions (topographical, geological, hydrological conditions, etc,..) for project area, precisely Analysis and simulation of reservoir 13

calculate relation curve between water level and discharge at tailrace of powerhouse. + Precisely calculate normal water level of hydropower reservoir based on calculation of surge water level to the end of reservoir caused by flood, to ensure no influence on electric energy efficiency and safety operation of Trung Son hydropower plant at upstream. + The spillway of Thanh Son hydropower project shall be designed in such a manner to ensure release safely checked flood discharge from Trung Son hydropower project in accordance with regulation specified in design standards and codes.. + Updating parameters such as upstream and downstream water level and power generation discharge of Trung Son and Hoi Xuan hydropower cascade projects (downstream side). Analysis, comparison to make accuracy of main parameters of project, especially installed capacity to ensure effective exploitation of project as well as electric power transmission network + Investigate, survey and establish compensation and resettlement plan for project, to ensure compliance with current relevant State regulation. 2.3 MAIN PARAMETERS OF TRUNG SON HYDROPOWER PROJECT TECHNICAL DESIGN STAGE In the technical design stage, the main tasks of project are defined as below: - With regards of electric power generation, installed capacity is Nlm = 260MW, annual electric energy Eo=1018.61 million kwh. - In terms of flood control, the reservoir flood control storage capacity is 150 million m 3 in which regular flood control storage capacity of 112 million m 3. Flood control period is 02 consecutive months of main flood season from 15 th July to 15 th September annually. Table 2-1: Main parameters of Trung Son hydropower project No. Description Unit Value I Basin characteristics 1 Catchment area Km 2 14660 2 Average long-term rainfalls X 0 mm 1 420 3 Average long-term flow (Qo) m 3 /s 235 4 Total annual flow Wo 10 6 m 3 7411 II Reservoir 1 Normal water level (NWL) m 2 Dead water level m 150 3 Water level before flood m 150 4 Flood storage volume Wpl 10 6 m 3 112 5 Reservoir storage volume corresponding to normal 10 6 m 3 348.53 Analysis and simulation of reservoir 14

No. Description Unit Value water level Wbt 6 Effective storage volume, flood storage volume Wpl 10 6 m 3 112.13 7 Dead storage volume Wc 10 6 m 3 236.40 8 Reservoir surface area corresponding to normal water level km 2 13.13 9 Flood peak discharge corresponding to frequencies - P= 0.1 % m 3 /s 13 400 - P= 0.5 % m 3 /s 10 400 - P= 1 % m 3 /s 9 - P= 5 % m 3 /s 6 III RCC dam 1 Dam crest elevation m 162.8 2 Dam crest length (L ) m 513.0 3 Max. dam height m 84.5 4 Dam crest width (b) m 8 5 Upstream slope (m) 0.35 6 Downstream slope (m) 0.65 IV Spillway 1 Spillway sill elevation m 145 2 Number of spillway cells 6 3 Spillway span BxH m 14x15 4 Orifice dimension of radial gate BxH m 14x15.5 5 Design flood released discharge P=0.5% m 3 /s 9 900 6 Checked flood released discharge P=0.1% m 3 /s 12 534 7 Dissipation structure Flip bucket V Waterway A Power intake gate 1 Power intake gate sill elevation m 135 2 Orifice dimension of trash rack nxbxh m 8x5.5x11 3 Orifice dimension of maintenance stop logs nxbxh m 1x5.5x5.5 4 Orifice dimension of operation gate nxbxh m 4x5.5x5.5 B Penstock 1 Penstock diameter m 5.5 2 Total length of one penstock m 229.57 3 Gradient slope of penstock % 13.95; 46.63 4 Penstock shell thickness mm 16-18 C Powerhouse characteristics 1 Turbine type Francis 2 Number of units 4 3 Installed capacity N lm MW 260 4 Firmed capacity N b MW 41. 5 Max. head H max m 72.02 Analysis and simulation of reservoir 15

No. Description Unit Value 6 Min. head H min m 51.32 7 Average head H tb m 66.30 8 Rated head H tt m 56.50 9 Max. discharge Q max through turbine m 3 /s 522 10 Average annual generated electricity E 0 10 6 KWh 1018.61 11 Number of power generated hours at installed capacity hour 3918 D Tailrace channel 1 Bottom width (b) m 79.7 2 Slope factor (m) 0.5 1.5 3 Gradient slope of channel bottom (i) 0.0001 4 Tailrace channel length (L) m 2.4 DATA FOR CALCULATION - Reservoir regulation curve: Coordinate on regulation curves of Trung Son hydropower project are shown in below table: Table 2-2: Water level on regulation curves of Trung Son hydropower project No. Month NWL(m) CXT PPH HCCN MWL(m) 1 June.0.00.00 150.00 150.0 2 July.0 150.00 150.00 150.00 150.0 3 Aug.0 150.00 150.00 150.00 150.0 4 Sept.0.00.00 150.00 150.0 5 Oct.0.00.00 157.00 150.0 6 Nov.0.00.00 156.60 150.0 7 Dec.0.00.00 155.50 150.0 8 Jan.0.00.00 154.30 150.0 9 Feb.0.00.00 153.10 150.0 10 Mar.0.00.00 152.50 150.0 11 Apr.0 159.00 158.20 151.70 150.0 12 May.0 158.00 155.40 150.50 150.0 Remark: + NWL: Normal water level. + CXT: Redundant discharge control regulation curve + PPH: Critical reservoir water level regulation curve + HCCN: Limit water supply regulation curve + MNC: Minimum water level. - 24 hours average flow to damsite of Trung Son hydropower project: see in chapter 1 Analysis and simulation of reservoir 16

- Reservoir characteristic curve: reservoir characteristic curve is set up on the map of 1/10,000 scale, established in 3 by Power Engineering Consulting Joint Stock Company 4 with aerial photograph method. The results are as below: Table 2-3: Reservoir characteristic curve of Trung Son hydropower project No. Elevation Z (m) Area F (km 2 ) Storage volume V (10 6 m 3 ) Remarks 1 85.0 0.0 0.0 2 90.0 0.3 0.6 3 95.0 0.5 2.6 4.0 1.1 6.4 5 105.0 1.7 13.2 6 110.0 2.2 22.7 7 115.0 2.8 35.1 8.0 3.5 50.9 9 125.0 4.4 70.6 10 130.0 5.1 94.1 11 135.0 5.9 121.6 12.0 7.0 153.9 13 145.0 8.2 191.9 14 150.0 9.6 236.4 MWL 15 155.0 11.1 288.1 16.0 13.1 348.5 NWL 17 165.0 15.2 419.3 18 170.0 17.6 501.2 - Relation curve between discharge and tailrace water level of Trung Son hydropower plant was set up based on hydraulic calculation formulas and river cross section, river bed longitudinal profile, investigation historical flood, The results are as below: No. Table 2-4:Relation curve between discharge and tailrace water level of Trung Son hydropower plant Discharge Q (m 3 /s) Water level Z (m) No. Discharge Q (m 3 /s) Water level Z (m) 1 0 85.90 17 300 90.51 2 10 86.71 18 350 90.76 3 20 87.27 19 400 90.98 4 30 87.82 20 500 91.39 5 40 88.37 21 600 91.78 6 50 88.67 22 700 92.14 7 60 88.81 23 0 92.48 Analysis and simulation of reservoir 17

No. Discharge Q (m 3 /s) Water level Z (m) No. Discharge Q (m 3 /s) Water level Z (m) 8 89.05 24 0 93.12 9 89.25 25 1500 94.48 10 89.42 26 0 95.66 11 150 89.66 27 3000 97.63 12 89.86 28 4000 99.41 13 89.98 29 5000.90 14 90.10 30 7000 103.82 15 250 90.26 31 00 105.06 16 2 90.42 32 00 107.38 - Efficiency of hydropower plant: Efficiency of unit at the calculation time depends on rated water head and discharge through turbine. In the calculation of daily hydro-energy operation of reservoir simulation, average efficiency of powerhouse is selected at 0.88. 2.5 CALCULATION, SIMULATION OF RESERVOIR The process of reservoir simulation calculation is executed according hydrological years, with hydrological calculation data obtaned in 50 years starting from June 1, 1975 to May 31, 7. On the basic of the data calculation as mentioned above, calculating hydroenergy simulation in two cases: - Without Thanh Son reservoir in downstream of Trung Son hydropower plant - With Thanh Son reservoir in downstream of Trung Son hydropower plant 2.6 WITHOUT THANH SON RESERVOIR IN DOWNSTREAM OF TRUNG SON HYDROPOWER PLANT (CASE 1) 2.6.1. Electric energy (Case 1) - The results of hydro energy calculation shown that the Energy difference between daily flow and monthy flow for calculation is about -4.6%. The results of calculation reflected variation in simulation operation of reservoir according to average daily flow and average monthy flow. Trung Son reservoir has small regulation coefficient = 0.015. Furthermore, the reservoir uses 2 months period as flood control for lowlands (from 15 th July to 15 th September annualy, reservoir water level at 150.0m elevation) hence regulation capacity of the reservoir in such period is not well enough. During flood control period, when natural inflow to reservoir is greater than maximum discharge for power generation, the redundant discharge will be released through the spillway (such Analysis and simulation of reservoir 18

redundant discharge shall not be considered as reservoir storage volume). The monthy average flow covers the average flow of incoming floods to reservoir, so, the redundant discharge through spillway of about 9% was calculated in reservoir discharge simulation. The daily average flow shown the incoming floods to the reservoir, so, the redundant discharge through spillway of 14% was calculated in reservoir discharge simulation. (greater than simulation of monthy average flow). According evaluation made by Design Consultant, the hydro energy simulation calculation results by daily average flow are more reliable than the hydro energy simulation calculation results by monthy average flow. Table 2-5: Results of hydro-energy calculation of Trung Son HPP using daily flow data, without Thanh Son reservoir in downstream of powerhouse ----------------------------------------------------------------- No Qs Qtbin Qx Htt N E ----------------------------------------------------------------- 1. 112.70 112.17.00 65.31 63.78 558.68 2. 184.43 165.79 14.50 67.44 93.59 819.86 3. 193.34 172.10 23.60 66.49 96.13 842.10 4. 290.12 225.92 60.81 66.89 125.47 1099.11 5. 234.88.85 33.33 67.35 114.49 2.94 6. 225.50 198.62 26.29 67.42 112.92 989.14 7. 285.93 232.26 53.08 67.02 130.67 1144.65 8. 265.17 222.07 42.51 67.15 125.65 1.68 9. 196.35 188.96 7.71 67.35 107.41 940.95 10. 259.87 211.02 47.38 67.16 117.19 1026.60 11. 205.69 183.57 21.52 67.59 103.84 909.67 12. 154.83 143.59 14.07 66.23 81.86 717.09 13. 186.31 168.94 13.41 66.88 94.47 827.54 14. 232.57 212.00 19.99 67.17 118.57 1038.68 15. 253.44.21 52.65 67.28 111.19 974.03 16. 249.88 206.54 42.76 67.27 116.24 1018.25 17. 341.71 233.54 107.58 66.94 130.34 1141.74 18. 228.45 212.48 15.39 67.32 121.21 1061.83 19. 274.81 214.58 59.65 67.19 121.91 1067.91 20. 233.28 199.87 32.82 67.40 113.95 998.16 21. 221.72 209.59 11.55 67.37 119.18 1043.98 22. 314.56 272.84 41.13 66.71 154.54 1353.73 23. 238.89.43 17.92 67.31 124.91 1094.21 24. 255.04 208.25 46.16 67.35 118.06 1034.22 25. 255.54 237.42 17.54 67.05 134.30 1176.43 26. 292.48 246.29 45.60 66.94 139.44 1221.46 27. 203.34 186.93 15.83 67.61 107.85 944.77 28. 228.78 214.81 13.38 67.31 122.77 1075.48 29. 249.90 218.34 30.97 67.31 125.13 1096.15 30. 207.13.24 6.31 67.48 114.14 999.85 31. 175.81 161.98 13.23 67.84 93.08 815.42 32. 175.43 158.94 15.91 67.84 91.86 4.68 33. 229.75 205.65 23.51 67.37 118.08 1034.39 34. 275.91 234.00 41.32 66.99 131.43 1151.34 35. 206.27 181.01 24.68 67.58 101.18 886.35 36. 155.24 149.25 5.40 67.94 85.82 751.76 37. 172.08 164.69 6. 67.83 94.78 830.31 38. 340.05 250.28 90.25 66.27 138.95 1217.23 39. 263.38 208.67 53.06 67.16 116.12 1017.22 40. 354.29 243.20 110.50 66.72 136.92 1199.39 41. 277.88 206.47 70.81 67.32 116.53 1020.81 42. 136.77 135.86 3.59 65.87 77.28 676.99 Analysis and simulation of reservoir 19

43. 226.20 203.78 18.60 67.30 115.69 1013.43 44. 249.11 221.13 27.39 67.29 124.98 1094.86 45. 292.05 248.47 42.99 66.86 139.14 1218.85 46. 333.96 269.39 63.98 66.56 151.24 1324.91 47. 242.04 223.27 18.18 67.27 128.20 1123.05 48. 248.41 218.69 29.38 67.29 123.05 1077.94 49. 264.07 206.05 57.20 67.24 116.84 1023.55 50. 161.65 146.66 17.94 67.84 82.89 726.09 ----------------------------------------------------------------- --------------------------------------------------------------------------------------------------- TT NWL MWL Vtb Vc Vhi Vplu Q0 Qtbin Qxa Qdb Qmax Hmax --------------------------------------------------------------------------------------------------- 1..00 150.00 348.53 236.40 112.13 112.13 237.14 203.15 33.40 66.53 504.0 71.07 --------------------------------------------------------------------------------------------------- TT Hmin Htb Nlm Ndb Ntb E0 Elu Eki Emua Ekho Hsd Beta --------------------------------------------------------------------------------------------------- 1. 48.05 64.85 260.00 41.75 114.91 6.57 649.00 357.57 549.13 457.44 3871..0150 --------------------------------------------------------------------------------------------------- In which: - Q s : Incoming discharge to Trung Son dam site (m 3 /s) - Q tbin : Discharge through turbine (m 3 /s) - Q x : Redundant discharge through spillway (m 3 /s) - H tt : Water head (m) - N: Capacity (MW) - E: Electric energy (million kwh) - NWL: Normal water level (m) - MWL: Minimum water level (m) - V tb : Total storage volume (million m 3 ) - V c : Dead storage (million m 3 ) - Q 0 : Annual average discharge to dam site (m 3 /s) - Q db : Firm discharge (m 3 /s) - Q max : Design discharge through turbine (m 3 /s) - H max : Maximum water head (m) - H min : Minimum water head(m) - H tb : Average water head (m) - N lm : Installed capacity (MW) - N b : Firm capacity (MW) - E 0 : Long-term average electric energy (million kwh) - E flood season : Long-term average electric energy in flood season (million kwh) - E dry flow season : Long-term average electric energy in dry flow season (million kwh) - E wet season : Long-term average electric energy in raining season (million kwh) - E dry season : Long-term average electric energy in dry season (million kwh) 2.6.2. Trung Son hydropower plant tailrace water level (case 1) - During the dry season days, the powerhouse is always operated with one turbine to ensure the release discharge to downstream to avoid great fluctuation in water level at downstream. The process of fluctuation in water level at downstream is considered as the most dangerous case when the power plant increases from 40% 50% capacity of one unit to installed capacity (N lm = 260MW), equivalent to discharge increasing from minimum discharge of one unit (about 63m 3 /s) to powerhouse design discharge of 522m 3 /s. During the operating process, it is not permitted to increase discharge to level which is greater than natural increase discharge before existence of reservoir. The maximum natural increased discharge taken place in range of < 700m 3 /s in period from 1957 to 7 as shown in below statistical table: Analysis and simulation of reservoir 20

Table 2-6: Process of maximum natural increased discharge (<700 m 3 /s) in period from 1957 to 7 Time Qday & night (m 3 /s) Q (m 3 Discharge increased /s) time (hour) Nov 13, 1966 124.37 Nov 14, 1966 675.3 551.0 12 Nov 15, 1966 653.3 Note Oct 16, 1985.2 Oct 17, 1985 690.2 470.0 12 Oct 18, 1985 632.9 Sept 14, 1998 208.0 Sept 15, 1998 664.8 456.7 24 Sept 16, 1998 757.8 July 23, 1989 201.3 July 24, 1989 653.1 451.8 24 July 25, 1989 1343.6 Oct 3, 1989 201.9 Oct 4, 1989 641.1 439.2 24 Oct 5, 1989 769.4 Sept 20, 1992 252.1 Sept 21, 1992 688.1 436.0 24 Sept 22, 1992 837.5 Oct 24, 1971 186.7 Oct 25, 1971 619.5 432.7 12 Oct 26, 1971 591.9 Nov 8, 1984 182.3 Nov 9, 1984 597.1 414.8 24 Nov 10, 1984 1300.2 Oct 12, 1988 174.6 Oct 13, 1988 574.6 400.0 24 Oct 14, 1988 1396.2 July 20, 1974 236.3 July 21, 1974 634.3 398.0 24 July 22, 1974 691.0 Average 445.0 - The table above shown that the hourly average natural increased discharge was about 40 m 3. So, in order to increase operating discharge from 63m 3 /s (50% maximum discharge of one unit) to 522 m 3 /s (design discharge of powerhouse), it is required at least 11 hours Analysis and simulation of reservoir 21

2.6.3. Specific characteristics of flow at power plant tailrace in daily period The plant tailrace daily average water level, natural daily average water level at river across section in powerhouse area, daily average discharge at tailrace of power plant, natural daily average discharge at river cross-section in powerhouse area are shown in below figures: Analysis and simulation of reservoir 22

Feasibility Study Average water level and natural water level at Trung Son hydropower plant (Plant tailrace without Thanh Son reservoir) 92.50 92.00 91.50 91.00 90.50 90.00 Water level (m) 89.50 89.00 88.50 0 25 50 75 125 150 175 225 250 275 300 325 350 375 400 Time (day) Plant tailrace water level Natural tailrace water level Analysis and simulation of reservoir 23

Feasibility Study Water level in little water year with frequency P=90% and natural water level at Trung Son hydropower plant (plant tailrace without Thanh Son reservoir) 94.00 93.50 93.00 92.50 92.00 91.50 91.00 90.50 Water level(m) 90.00 89.50 89.00 88.50 0 25 50 75 125 150 175 225 250 275 300 325 350 375 400 Time (day) Plant tailrace water level Natural water level Analysis and simulation of reservoir 24

Feasibility Study 95.00 Water level in much water year with frequency P=10% and natural water level at Trung Son hydropower plant (In case plant tailrace without Thanh Son reservoir) 94.00 93.00 92.00 91.00 Water level (m) 90.00 89.00 88.00 0 25 50 75 125 150 175 225 250 275 300 325 350 375 400 Time (day) Plant tailrace water level Natural water level Analysis and simulation of reservoir 25

Feasibility Study Average discharge and natural discharge at Trung Son plant tailrace (In case Plant tailrace without Thanh Son reservoir) 0.0 700.0 600.0 500.0 400.0 300.0 Discharge (m 3 /s).0.0 0.0 0 25 50 75 125 150 175 225 250 275 300 325 350 375 400 Time (day) Discharge at plant tailrace Natural discharge at plant tailrace Analysis and simulation of reservoir 26

Feasibility Study Discharge in little water year with frequency P=90% and natural discharge at Trung Son plant tailrace (In case plant tailrace without Thanh Son reservoir) 1 0 0 600 Discharge (m 3 /s) 400 0 0 25 50 75 125 150 175 225 250 275 300 325 350 375 400 Time (day) Discharge at plant tailrace Natural discharge at plant tailrace Analysis and simulation of reservoir 27

Feasibility Study 0 Discharge in much water year with P=10% and natural discharge at Trung Son hydropower plant tailrace (In case plant tailrace without Thanh Son reservoir) 0 1 0 0 600 Discharge (m 3 /s) 400 0 0 25 50 75 125 150 175 225 250 275 300 325 350 375 400 Time(day) Discharge at plant tailrace Natural discharge at plant tailrace Analysis and simulation of reservoir 28

Feasibility Study 2.6.4. Specific characteristics of flow at power plant tailrace in hourly period For estimation of flow specific characteristics fluctuation level (water level, discharge) in hourly period at river cross-section at powerhouse area, the Design Consultant calculated some operation cases, particularly as below: Table 2-7:Operation of Trung Son hydropower plant in case daily average discharge of 234 m 3 /s released to downstream Discharge(m 3 /s) Hour Unit 1 Unit 2 Unit 3 Unit 4 Total Increasing 1 63 63 2 63 63 3 63 63 4 63 63 5 63 63 6 63 63 7 63 63 8 126 126 63 9 126 126 10 126 126 11 126 63 189 63 12 126 63 63 252 63 13 126 126 63 315 63 14 126 126 126 378 63 15 126 126 126 378 16 126 126 126 378 17 126 126 126 63 441 63 18 126 126 126 126 504 63 19 126 126 126 126 504 20 126 126 126 126 504 21 126 126 126 126 504 22 126 63 63 63 315-189 23 63 63-252 24 63 63 Average 102 55 50 26 234 Analysis and simulation of reservoir 29

Feasibility Study Table 2-8: Operation of Trung Son hydropower plant in case daily average discharge of m 3 /s released to downstream Discharge(m 3 /s) Hour Unit 1 Unit 2 Unit 3 Unit 4 Total Increasing 1 63 63 2 63 63 3 63 63 4 63 63 5 63 63 6 63 63 7 63 63 8 63 63 9 126 126 63 10 126 126 11 126 126 12 126 126 13 126 126 14 126 63 189 63 15 126 63 63 252 63 16 126 126 63 315 63 17 126 126 63 63 378 63 18 126 126 126 63 441 63 19 126 126 126 126 504 63 20 126 126 126 126 504 21 126 126 126 126 504 22 126 63 63 63 315-189 23 63 63 63 189-126 24 63 63-126 Average 42 34 24 Analysis and simulation of reservoir 30

Feasibility Study Table 2-9: Operation of Trung Son hydropower plant in case daily average discharge of 155 m 3 /s released to downstream Discharge(m 3 /s) Hour Unit 1 Unit 2 Unit 3 Unit 4 Total Increasing 1 63 63 2 63 63 3 63 63 4 63 63 5 63 63 6 63 63 7 63 63 8 63 63 9 63 63 10 63 63 11 63 63 12 126 126 63 13 126 126 14 126 126 15 126 63 189 63 16 126 126 252 63 17 126 126 63 315 63 18 126 126 126 378 63 19 126 126 126 378 20 126 126 126 378 21 126 126 126 378 22 126 63 63 252-126 23 63 63-189 24 63 63 Average 92 37 26 155 Analysis and simulation of reservoir 31

Feasibility Study Table 2-10: Operation of Trung Son hydropower plant in case daily average discharge of 102 m 3 /s released to downstream Discharge(m 3 /s) Hour Unit 1 Unit 2 Unit 3 Unit 4 Total Increasing 1 63 63 2 63 63 3 63 63 4 63 63 5 63 63 6 63 63 7 63 63 8 63 63 9 63 63 10 63 63 11 63 63 12 63 63 13 63 63 14 126 126 63 15 126 126 16 126 126 17 126 63 189 63 18 126 126 252 63 19 126 126 252 20 126 126 252 21 63 63 126-126 22 63 63-63 23 63 63 24 63 63 Average 81 21 102 Analysis and simulation of reservoir 32

2.6.5. Trung Son hydropower reservoir water level fluctuation (case1) Feasibility Study - Regulation on maximum water level of reservoir: from 15 th July to 15 th September annually, maximum water level of reservoir is regulated at minimum water level of 150.0m to control flood for lowlands (according regulation on water level of reservoir specified in Trung Son hydropower reservoir operation rules which was approved by Ministry of Industry and Trade). According stability calculation of the reservoir banks (in some areas with possibility of reservoir banks collapse and sliding), it is shown that the requirement on process of draining water level in reservoir should not be greater than 0.7m/day and night, therefore in the hydro energy calculation, the time requested for draining water level in reservoir from NWL=.0m down MWL=150.0m should be over 15 days. In the actual reservoir operation process, depending on incoming flow discharge in initial flood season, reservoir draining to lower water level should be made suitably, to ensure minimum redundant discharge and increase electricity generation output. The actual process of draining reservoir water level can be twenty days to drain water level from.0m down to water level at 150.0m. - The generation discharge include natural incoming discharge to reservoir and discharge supplied from reservoir. The reservoir discharge supply potential is shown in below table: Table 2-11: Discharge supply potential from Trung Son hydropower reservoir No. Elevation Z (m) Surface area of reservoir F (km 2 ) Storage capacity of reservoir V (10 6 m 3 ) Discharge supply from the reservoir Q câp (m 3 /s) 1.0 13.13 348.5 2 159.0 12.72 336.4.0 3 158.0 12.31 324.3.0 4 157.0 11.90 312.2.0 5 156.0 11.49 300.2.0 6 155.0 11.08 288.1.0 7 154.0 10.78 277.7 119.6 8 153.0 10.49 267.4 119.6 9 152.0 10.19 257.1 119.6 10 151.0 9.90 246.7 119.6 11 150.0 9.60 236.4 119.6 Remarks - The process of reservoir impounding shall begin from 15 th September annually. The reservoir impounding is allowable to full water level from time to time as possible because the erosion to reservoir banks shall not be taken place during process of impounding water Analysis and simulation of reservoir 33

Feasibility Study The water level curve process with frequency 90% of Trung Son hydropower reservoir ( Downstream without Thanh Son reservoir) 161.0.0 159.0 158.0 157.0 156.0 155.0 154.0 Water level (m) 153.0 152.0 151.0 150.0 149.0 0 25 50 75 125 150 175 225 250 275 300 325 350 375 400 Time (day) Analysis and simulation of reservoir 34

Feasibility Study The water level curve process with frequency 10% of Trung Son hydropower reservoir ( Downstream without Thanh Son reservoir) 161.0.0 159.0 158.0 157.0 156.0 155.0 154.0 Water level (m) 153.0 152.0 151.0 150.0 149.0 0 25 50 75 125 150 175 225 250 275 300 325 350 375 400 Time (day) Analysis and simulation of reservoir 35

Feasibility Study The avearge water level curve process of Trung Son hydropower reservoir ( Downstream without Thanh Son reservoir) 161.0.0 159.0 158.0 157.0 156.0 155.0 154.0 Water level (m) 153.0 152.0 151.0 150.0 149.0 0 25 50 75 125 150 175 225 250 275 300 325 350 375 400 Time (day) Analysis and simulation of reservoir 36

2.7 DOWNSTREAM WITH THANH SON RESERVOIR (CASE 2) 2.7.1. Electric energy (case 2) - In case with Thanh Son Hydropower reservoir (Normal Water Level = 89.0m) located downstream of Trung Son hydro powerhouse, the toe of Trung Son hydro powerhouse is submerged. The hydro energy calculation results show that the energy decreases inconsiderable in compared with the case of insubmerged powerhouse toe (0.08 million KWh). See details as below: Table 2-12: Hydro energy calculation results of Trung Son using daily flow data, with Thanh Son reservoir dowstream of Trung Son HPP ----------------------------------------------------------------- No Qs Qtbin Qx Htt N E ----------------------------------------------------------------- 1. 112.70 112.17.00 65.13 63.71 558.07 2. 184.43 165.79 14.50 67.39 93.57 819.64 3. 193.34 172.10 23.59 66.44 96.11 841.90 4. 290.12 225.93 60.81 66.87 125.46 1099.06 5. 234.88.84 33.32 67.34 114.48 2.84 6. 225.50 198.62 26.29 67.40 112.91 989.06 7. 285.93 232.26 53.07 67.01 130.67 1144.65 8. 265.17 222.08 42.50 67.14 125.64 1.61 9. 196.35 188.98 7.71 67.32 107.41 940.89 10. 259.87 211.01 47.38 67.14 117.17 1026.42 11. 205.69 183.58 21.52 67.58 103.84 909.60 12. 154.83 143.59 14.06 66.19 81.84 716.88 13. 186.31 168.94 13.40 66.84 94.45 827.34 14. 232.57 212.00 19.99 67.14 118.56 1038.55 15. 253.44.22 52.64 67.26 111.18 973.95 16. 249.88 206.55 42.75 67.26 116.24 1018.22 17. 341.71 233.54 107.57 66.93 130.34 1141.75 18. 228.45 212.48 15.38 67.31 121.21 1061.81 19. 274.81 214.58 59.64 67.18 121.90 1067.88 20. 233.28 199.87 32.82 67.40 113.95 998.18 21. 221.72 209.59 11.55 67.36 119.18 1043.98 22. 314.56 272.85 41.13 66.71 154.54 1353.75 23. 238.89.43 17.92 67.29 124.90 1094.15 24. 255.04 208.25 46.15 67.33 118.05 1034.14 25. 255.54 237.42 17.54 67.04 134.29 1176.39 26. 292.48 246.30 45.59 66.94 139.44 1221.47 27. 203.34 186.93 15.82 67.60 107.85 944.73 28. 228.78 214.82 13.38 67.31 122.77 1075.49 29. 249.90 218.34 30.96 67.31 125.13 1096.15 30. 207.13.24 6.31 67.48 114.13 999.81 31. 175.81 161.99 13.22 67.83 93.08 815.37 32. 175.43 158.94 15.91 67.82 91.85 4.58 33. 229.75 205.66 23.51 67.36 118.08 1034.38 34. 275.91 234.01 41.31 66.99 131.43 1151.34 35. 206.27 181.01 24.68 67.56 101.17 886.29 36. 155.24 149.25 5.40 67.91 85. 751.62 37. 172.08 164.70 6. 67.81 94.77 830.22 38. 340.05 250.32 90.25 66.24 138.95 1217.24 39. 263.38 208.65 53.05 67.13 116.09 1016.92 40. 354.29 243.20 110.50 66.72 136.92 1199.41 41. 277.88 206.48 70.81 67.30 116.52 1020.74 42. 136.77 135.86 3.59 65.79 77.24 676.64 43. 226.20 203.79 18.60 67.29 115.68 1013.37 44. 249.11 221.14 27.39 67.29 124.98 1094.83 45. 292.05 248.48 42.98 66.85 139.14 1218.83 46. 333.96 269.40 63.97 66.56 151.25 1324.94 47. 242.04 223.27 18.18 67.27 128.20 1123.06 48. 248.41 218.70 29.38 67.27 123.04 1077.86 49. 264.07 206.06 57.19 67.22 116.83 1023.43 50. 161.65 146.67 17.93 67. 82.87 725.91 ----------------------------------------------------------------- --------------------------------------------------------------------------------------------------- TT NWL MNL Vtb Vc Vhi Vplu Q0 Qtbin Qxa Qdb Qmax Hmax --------------------------------------------------------------------------------------------------- 1..00 150.00 348.53 236.40 112.13 112.13 237.14 203.16 33.40 65.84 504.0 70.95 --------------------------------------------------------------------------------------------------- TT Hmin Htb Nlm Ndb Ntb E0 Elu Eki Emua Ekho Hsd Beta --------------------------------------------------------------------------------------------------- 1. 48.05 64.85 260.00 41.25 114.90 6.49 649.01 357.48 549.15 457.34 3871..0150 --------------------------------------------------------------------------------------------------- Analysis and simulation of reservoir 37

In which: - Q s : Discharge coming to dam site of Trung Son (m 3 /s) - Q tbin : Discharge through turbine (m 3 /s) - Q x : Redundant discharge release to spillway(m 3 /s) - H tt : Water head calculation (m) - N: Capacity (MW) - E: Electric energy (million kwh) - NWL: Normal water level (m) - MWL: Minimum water level (m) - V tb : Total storage capacity (million m 3 ) - V c : Dead storage (million m 3 ) - Q 0 : Annual average discharge to dam site(m 3 /s) - Q db : Firm discharge (m 3 /s) - Q max : Design discharge through powerhouse(m 3 /s) - H max : Maximum water head (m) - H min : Minimum water head (m) - H tb : Average water head (m) - N lm : Installed capacity (MW) - N b : Firm capacity(mw) - E 0 : Long-term average electric energy (million kwh) - E flood season : Long-term average electric energy in flood season (million kwh) - E dry flow season : Long-term average electric energy in dry flow season (million kwh) - E wet season : Long-term average electric energy in raining season (million kwh) - E dry season : Long-term average electric energy in dry season (million kwh) 2.7.2. Trung Son hydropower Plant tailrace water level (Case 2) - The catchment basin area calculate to damsite of Trung Son HPP is 14660 km 2, to damsite of Thanh Son HPP is 14760 km 2, middle catchment basin area is km 2 - Downstream of Trung Son hydropower plant is Thanh Son hydropower plant, so Trung Son Hydropower Plant tailrace water level is always higher than minimum water level of Thanh Son hydropower plant. The Thanh Son HPP is design with dam combined with spillway in Ma river and dam toe type powerhouse, so the water level fluctuation in reservoir is at small range. The Thanh Son HPP shall be operated synchronously with Trung Son HPP. As of present time, Thanh Son hydropower project is in feasibility study stage, the reservoir parameters such as NWL; MWL; N lm have not yet been defined presisely. In case the reservoir of Thanh Son HPP has 24 hours regulation storage volume, it is allowable to release discharge from 63m 3 /s up to 522m 3 /s in short time from Trung Son HPP (as allowable condition of equipment of powerhouse) Analysis and simulation of reservoir 38

2.7.3. Trung Son HPP reservoir water level fluctuation (case 2) - In case with Thanh Son reservoir downstream of Trung Son HPP reservoir water levels fluctuation shall be same as in case without Thanh Son reservoir. The possibility of reservoir impounding to maximum water level is allowable. The reservoir water level drawn-down allowable condition should not be more than 0.7m/24 hours. In the process of operation, depending on hydrological condition (incoming flow to damsite) water draining capacity shall be calculated in such a manner to ensure minimum discharge released through spillway and maximum electric energy generation output. Analysis and simulation of reservoir 39

Chapter 3: WATER SUPPLY DEMAND FOR DOWNSTREAM 3.1 WATER DEMAND AT DOWNSTREAM 3.1.1. Scope of water demand Water demand at Ma River downstream was accessed in many previous plans by Ministry of Agriculture and Rural Development (MARD). According to report named General updating Irrigation planning of cascades to develop economy at downstream of Ma river basin which was conducted by Water Resource Planning Institute, under MARD, main purposes of projects on Ma River are electric generation and flood control. Main purposes of projects on Chu River are water supply and flood control. This does not mean downstream of Trung Son project has no water during dry season. Impounding period of Trung Son reservoir will only take place a short time (4 days in flood season). Water demand at downstream, however, of Trung Son project, from P/H to confluence of Ma River and Xia stream (20km) and from Xia stream to confluence of Ma River and Luong tributary (25km), needs to be evaluated. - River reach from P/H to confluence of Ma River and Xia stream (20km: There are villages and local people living along both two banks. Water source for living and irrigation is mainly groundwater and streams. They were not use water from Ma River. For navigation on river: Along river bank, access road was built from Co Luong to dam site. Therefore, environmental flow on this river reach mainly secures flora and fauna such as land cover along banks, buffalo, cow, etc, and aquatic life. Result of monthly flow calculation is shown in Table below: Table 3-1: Average monthly flow within area from dam route to Xia stream. Month Jan Feb Mar Apr May June July Aug Sept Oct Nov Dec Q o (m 3 1.74 1.52 1.45 1.60 2.63 4.04 5.14 7.28 9.9 7.84 4.16 2.23 /s) - River reach from Xia stream to confluence of Ma River and Luong tributary (25km): There are many tributaries and large stream which has high flow supply for Ma River s flow such as Xia stream, Luong and Lung tributaries, Chu River. Xia catchment area is 249km2 with 5.21 m3/s of annual flow, 8.07 m3/s of average flood flow, and 6.5 m3/s when diversion culvert is blocked (July). Table 3-2: Average monthly flow of Xia stream. Month Jan Feb Mar Apr May June July Aug Sept Oct Nov Dec Q o (m 3 /s) 2.20 1.92 1.83 2.02 3.33 5.10 6.50 9.20 12.5 9.91 5.25 2.82 Luong tributary has 970 km 2 of catchment area with 23 m 3 /s of annual flow and 40 m 3 /s of average flood flow. Therefore, abundant water resource can be supplied to this river section. Moreover, National Highway No. 15 (QL15) along river bank was built so transportation does not be affected during reservoir impounding (3-5days on Appendix 40

July) and flood season. Environmental flow is always secured on Ma river after Luong tributary. Hence, only environmental flow within river section from downstream of dam route to confluence with Xia stream is considered. Trung Son HPP Xia Catchment Area F=249 km 2 3.1.2. Ma River Xia Stream Interstream Area F=209 km 2 3.1.3. Water demand for Industry and daily uses. Water demand for Industry and daily uses is considered up to 2020. According to report named General updating Irrigation planning of cascades to develop economy at downstream of Ma river basin, water demand for these fields as below: Table 3-3: Water demand for Industry and daily uses No Location Demand (m 3 /s) Note 1 Trung S n town 0.05 2 Quan Hoá town 0.05 3 Bá Th c town 0.10 4 C m Th y town 0.10 Total 0.30 Appendix 41